Some drain pipes which are used are salt glazed sewer pipes and have an inside diameter of four inches (100 mm) or thereabouts, and are constructed to a standard. Most television cameras are of such length that they are not able to negotiate standard bends or tees in pipes of this dimension. A television camera has associated with it two separate circuits, namely a scanning circuit and a signalling amplifier circuit, both of which are usually adjacent the television camera. This results in bulky equipment which cannot be used in drain pipes, and to reduce size it has been proposed to locate the signal amplifier above ground level and connect it to the camera and scanning circuit by a co-axial television cable. This must be of sufficient length to allow the camera to be drawn into a drain pipe, and a cable of less than one hundred feet (thirty meters) would be quite inconvenient. However, such a TV cable is not capable of delivering the signals with the required degree of clarity. It is estimated that about 50% of clarity is lost because of this disability.